My MIL has asked me how to tell if the King Arthur flour she bought last winter is still good, even though it's past the sell by date. She didn't realize she could put it in the freezer so it's been kept in their basement (cool). It's unbleached but I don't think that would affect it's preservation (or lack of).
Would old flour just not rise as well (protein network breaks down)? If it were me I'd just use it but I was hoping to give MIL a more definitive answer.